Known turbine generators employ internal air cooling systems to circulate cooling air within the machine. Cooling air circulation is directed by combinations of one or more of cooling channels, vanes, the centrifugal forces generated by the rotating rotor, convective thermal gradients and forced air fans. An exemplary known turbine generator 20 is shown in FIGS. 1 and 2. The generator's generally annular stator 22 has plurality of stator axial slots 23 circumferentially aligned about the stator bore 24. Among other places within the generator cooling air flows within an annular air gap 26 between the stator bore 26 and the rotating rotor 28. A plurality of axially aligned composite airflow baffles 30 circumscribe the stator bore and establish cooling airflow zones in the air gap 26 that are bounded by the composite baffles. Each composite baffle 30 is formed by adjoining axially aligned circumferential baffle sector portions 32 are supported by a plurality of air baffle trains 34 that are oriented in corresponding stator slots about the stator bore 24 circumference. Each baffle train 34 comprises a plurality of baffle sector wedges 36 that support individual baffle sector portions 32, which are axially separated by baffle wedge spacers 38, so that the ultimate spacing between baffle sector portions corresponds to the composite airflow baffle 30 locations within the stator bore 24 and air gap 26. The baffle sector wedges 36 and baffle wedge spacers 38 define commonly aligned through bores 40 that receive baffle wedge cable 42.
The wedge strings 36, 30 in each baffle train 34 are restrained in abutting contact by tensioning the baffle wedge cable 42 (analogous to a rigid bead chain) with a baffle wedge cable tensioner 44 that is coupled to the generator structure. The individual wedges 36, 38 must be trimmed to align the baffle sectors 32 in the various baffle trains 34 within the rotor slots, for proper desired composite baffle 30 orientation. Wedge trimming usually requires a number of attempts as any one wedge within a baffle train 34 impacts location of other wedges in the train. Cable tensioning also impacts ultimate linear location of each baffle sector within the train.
The wedges 36, 38 are constructed of cotton reinforced phenolic resin. That material has dimensional consistency challenges impacted by water absorption, shrinkage and thermo-mechanical creep. Over time and during generator operational service the baffle trains 34 loosen, causing slack between the wedges 36, 38 and resultant axial and/or radial misalignments of the baffle sectors 32. For example, baffle wedge 36 shrinkage can result in radial slop within the stator slot 23, which can vary the desired gap between the baffle sector 32 and the rotor 28. Either type of wedge 36 or 38 axial shrinkage alters axial orientation of the baffle sectors 32. Dimensional changes in any one of the wedges 36 or 38 in the baffle train 34 changes orientation of all of the other wedges in the train.